Why do penguins waddle?

Answer 1

because of the way the ilia is fused to the synsacrum of the bird, and the birds back bone is flexible

and because it's the only way it can walk

Answer 2

Penguins waddle because their legs are set far back on their bodies and they have a round shape, which makes walking more awkward on land. This waddling movement helps them move more efficiently and maintain balance while on land.